Mask of Riddles

T, Sacrifice this artifact: You gain life equal to the total life lost by all players this turn. (Damage causes loss of life.)

T: Untap another target permanent.

Whenever another creature dies, you may put a +1/+1 counter on this creature. Remove a +1/+1 counter from this creature: It deals 1 damage to any target.

Devour 1 (As this creature enters, you may sacrifice any number of creatures. It enters with that many +1/+1 counters on it.)

T: Tap target creature unless its controller pays 2 life.

Whenever this creature becomes blocked, defending player loses 4 life.

When this creature enters, it deals damage to target player equal to the number of nonbasic lands that player controls. Unearth 5BR (5BR: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Vigilance, haste